This invention relates in general to knives, and relates in particular to a folding knife equipped with a simple lever mechanism for unfolding or opening the blade.
The traditional folding knife, sometimes also referred to as a pocket knife, has one or more blades, pivotably mounted within a housing or casement. To prevent accidental opening of the knife, each blade typically is biased in the closed position by a mechanism such as a spring or detent. To open the blade, the user must insert a thumbnail of one hand into a notch or groove provided for that purpose near the back edge of the blade, and manually rotate the blade around its pivot point at one end of the knife body while holding the body with the other hand. This opening technique can be difficult to accomplish, particularly for those having short thumbnails or for a handicapped person who may not have full use of both hands, or with knives whose blade pivot mechanism is relative stiff. Moreover, in some jobs, such as fisherman or paratrooper, it is essential to be able to open a knife with one hand while the other is otherwise occupied.
Folding knives with various mechanisms for opening or assisting with opening the blade are known in the art. For example, U.S. Pat. No. 4,177,560 discloses a knife with an action controlling the rate at which a switchblade knife opens, creating a safer one-hand opening knife. U.S. Pat. No. 4,719,700 discloses a one-hand opening knife actuated by a sliding lever interconnected with the blade via a complex set of gears. This suffers from being expensive to manufacture, and difficult to operate as the leverage factor is low. U.S. Pat. No. 4,893,409 displays a one-hand opening knife operated via button on the side which engages and disengages the blade from the handle. While this reduces opening force due to a spring or detent blade retainer, it does not allow the knife to be opened with one hand while keeping the hand in the normal operating position. This requires either using two hands, keeping the operating hand in its normal position, or rearranging ones grip on the knife for opening it. U.S. Pat. No. 5,331,741 discloses a folding knife with a lever opening the blade via a complex mechanism of gears and cams.
These arrangements all have various practical disadvantages, among which is the expense of manufacture, the fragility of the parts with respect to wear tear and the stress of opening and using the knife. Further, all require either two hands to operate, shifting the knife position to operate, or a contrary motion of the hands or fingers to operate. For example, the knife shown in U.S. Pat. No. 5,331,741 requires the thumb of the right hand (shown designed only for a right-handed person) to move away from its operating position to open the knife. Additionally, this design shows an actuation lever which, in the blade-open position, intrudes into the grip of the knife it what appears to be an uncomfortable way.
Common to the existing art is a one-hand-opening knife where a conventional folding knife design is enhanced with the provision of a button, or protrusion on the blade which permits thumb purchase and one-handed blade opening. This suffers the disadvantage of such protuberance, being permanently affixed to the blade, intruding into the working area of the knife, limiting the depth of its penetration and cut.